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| United States Patent |
5,120,359
|
|
Uzukawa
, et al.
|
June 9, 1992
|
Erasable ink compositions
Abstract
The present invention provides:
(1) an ink composition erasable with a rubber eraser, the composition
comprising 1 to 50% of a pigment, 3 to 50% of a resin having a
film-forming temperature of 40.degree. C. or higher, 0.5 to 50% of an
organic solvent and 7 to 60% of water, based on the weight of the ink
composition;
(2) an ink composition erasable with a rubber eraser, the composition
comprising 2 to 90% of a pigment coated with a resin having a film-forming
temperature of 40.degree. C. or higher, 0.5 to 30% of an organic solvent
and 0.5 to 30% of water, based on the weight of the ink composition; and
(3) an ink composition erasable with a rubber eraser, the composition
comprising 2 to 90% of a pigment coated with a resin having a film-forming
temperature of 40.degree. C. or higher, 1.5 to 55% of an emulsion
(calculated as solids), 0.5 to 30% of an organic solvent and 4.0 to 60% of
water, based on the weight of the ink composition.
| Inventors:
|
Uzukawa; Shingo (Kashiwara, JP);
Shoji; Yukito (Suita, JP)
|
| Assignee:
|
Sakura Color Products Corporation (Osaka, JP)
|
| Appl. No.:
|
434678 |
| Filed:
|
October 26, 1989 |
| PCT Filed:
|
February 22, 1989
|
| PCT NO:
|
PCT/JP89/00181
|
| 371 Date:
|
October 26, 1989
|
| 102(e) Date:
|
October 26, 1989
|
| PCT PUB.NO.:
|
WO89/08134 |
| PCT PUB. Date:
|
September 8, 1989 |
Foreign Application Priority Data
| Feb 26, 1988[JP] | 63-45341 |
| Feb 26, 1988[JP] | 63-45342 |
| Current U.S. Class: |
106/31.25; 106/31.64; 106/31.86; 106/499; 106/500; 523/160; 523/161; 523/205; 524/560; 524/561; 524/562; 524/563; 524/575; 524/577 |
| Intern'l Class: |
C09D 011/10 |
| Field of Search: |
106/20,23,499,500
523/161,160,205,377,388
524/560,561,562,563,575,577
|
References Cited
U.S. Patent Documents
| 3458804 | Jul., 1969 | Wolf et al. | 106/500.
|
| 3925094 | Dec., 1975 | Papenfuss et al. | 106/500.
|
| 3925096 | Dec., 1975 | Karkov | 524/563.
|
| 4014844 | Mar., 1977 | Vidal et al. | 524/560.
|
| 4036652 | Jul., 1977 | Rothmayer | 524/560.
|
| 4235768 | Nov., 1980 | Ritter et al. | 524/560.
|
| 4365035 | Dec., 1982 | Zabiak | 523/160.
|
| 4525216 | Jun., 1985 | Nakanishi | 106/30.
|
| 4530961 | Jul., 1985 | Nguyen et al. | 523/160.
|
| 4636258 | Jan., 1987 | Hayashi et al. | 523/160.
|
| 4665107 | May., 1987 | Micale | 523/161.
|
| 4680058 | Jul., 1987 | Shimizu et al. | 523/160.
|
| 4687789 | Aug., 1987 | Gonnett et al. | 524/560.
|
| 4713411 | Dec., 1987 | Kanou et al. | 524/560.
|
| 4833197 | May., 1989 | Schelhaas et al. | 523/160.
|
Primary Examiner: Dixon, Jr.; William R.
Assistant Examiner: Klemanski; Helene
Attorney, Agent or Firm: Larson and Taylor
Claims
We claim:
1. An ink composition erasable with a rubber eraser after writing, the
composition comprising, based on the weight of the ink composition, 1 to
50% of a pigment, 3 to 50% of a water insoluble resin having a
film-forming temperature of 40.degree. C. or higher, 0.5 to 50% of at
least one organic solvent selected from the group consisting of alkylene
glycols, dialkylene glycols, polyalkylene glycols and glycerins, and 7 to
60% of water.
2. An ink composition according to claim 1 wherein the resin is at least
one of acrylic resins, acryl-styrene copolymer resins, ethylene-vinyl
acetate-vinyl chloride copolymer resins, acryl-vinyl acetate resins,
carboxylated butadiene-styrene rubber and styrene resins.
3. An ink composition according to claim 1 wherein the resin has a
film-forming temperature of 50.degree. C. or higher.
4. An ink composition according to claim 1 wherein the pigment accounts for
5 to 30%, the resin for 10 to 45%, the organic solvent for 10 to 30% and
the water for 7 to 60% in the whole weight of the ink composition.
5. An ink composition erasable with a rubber eraser after writing, the
composition comprising, based on the weight of the ink composition, 2 to
90% of a pigment coated with a water insoluble resin having a film-forming
temperature of 40.degree. C. or higher, 0.5 to 30% of at least one organic
solvent selected from the group consisting of alkylene glycols, dialkylene
glycols, polyalkylene glycols and glycerins, and 0.5 to 30% of water.
6. An ink composition according to claim 5 wherein the resin is at least
one of acrylic resins, acryl-styrene copolymer resins, ethylene-vinyl
acetate-vinyl chloride copolymer resins, acryl-vinyl acetate resins,
carboxylated butadiene-styrene rubber and styrene resins.
7. An ink composition according to claim 5 wherein the resin used for
coating the pigment has a film-forming temperature of 50.degree. C. or
higher.
8. An ink composition according to claim 5 wherein the pigment and the
resin are present in a ratio of 40-95 : 60-5 of the former to the latter
in 100 parts of the resin-coated pigment.
9. An ink composition according to claim 5 wherein the particles of
resin-coated pigment have a mean particle size of 0.1 to 10 .mu.m.
10. An ink composition according to claim 5 wherein the resin-coated
pigment accounts for 10 to 70%, the organic solvent for 1 to 20% and the
water for 0.5 to 30% in the whole weight of the ink composition.
11. An ink composition erasable with a rubber eraser after writing, the
composition comprising, based on the weight of the ink composition, 2 to
90% of a pigment coated with a water insoluble resin having a film-forming
temperature of 40.degree. C. or higher, 1.5 to 55% of water insoluble
emulsion (calculated as solids), 0.5 to 30% of at least one organic
solvent selected from the group consisting of alkylene glycols, dialkylene
glycols, polyalkylene glycols and glycerins, and 4.0 to 60% of water.
12. An ink composition according to claim 11 wherein the resin is at least
one of acrylic resins, acryl-styrene copolymer resins, ethylene-vinyl
acetate-vinyl chloride copolymer resins, acryl-vinyl acetate resins,
carboxylated butadiene-styrene rubber and styrene resins.
13. An ink composition according to claim 11 wherein the pigment and the
resin are present in a ratio of 40-95 : 60-5 of the former to the latter
in 100 parts of the resin-coated pigment.
14. An ink composition according to claim 11 wherein the particles of
resin-coated pigment have a mean particle size of 0.1 to 10 .mu.m.
15. An ink composition according to claim 11 wherein the resin-coated
pigment accounts for 10 to 70%, the emulsion for 2 to 50% (calculated as
solids), the organic solvent for 0.5 to 30% and the water for 4 to 60%.
Description
The present invention relates to ink compositions and more particularly to
ink compositions erasable with a rubber eraser after writing.
PRIOR ART AND ITS PROBLEMS
Ink compositions erasable with a rubber eraser after writing (hereinafter
referred to as "erasable ink") are known. For example, Japanese Unexamined
Patent Publication No.59-223,769 discloses an "ink composition
characterized in that it is prepared by uniformly dispersing a pigment
selected from carbon black and aniline black in an aqueous medium having
dissolved therein polyethylene oxide in the presence of a surfactant
containing polyoxyethylene groups". However, the disclosed erasable ink is
poor in stability, unsatisfactory in erasability, and difficult to erase
in a long period after writing. Other erasable inks of various
compositions heretofore proposed are insufficient in at least one of shelf
life, erasability, fluidity and the like required of erasable inks, and
thus all of them fail to achieve the desired results.
MEANS FOR RESOLVING THE PROBLEMS
In view of the foregoing present situation of the prior art, we conducted
extensive research and found that the compositions which contain a resin
having a specific minimum film-forming temperature or glass transition
point (hereinafter referred to merely as "film-forming temperature") can
alleviate the problems of conventional erasable inks to a great extent.
According to the present invention, there is provided the following
erasable ink:
(1) an ink composition erasable with a rubber eraser, the composition
comprising 1 to 50% of a pigment, 3 to 50% of a resin having a
film-forming temperature of 40.degree. C or higher, 0.5 to 50% of an
organic solvent and 7 to 60% of water, based on the weight of the ink
composition (hereinafter referred to as "composition I").
Our research revealed that the ink compositions which contain pigment
particles coated with a resin having a specific film-forming temperature
can also sufficiently mitigate the problems of conventional erasable inks.
According to the present invention, there are also provided the following
ink compositions:
(2) an ink composition erasable with a rubber eraser, the composition
comprising 2 to 90% of a pigment coated with a resin having a film-forming
temperature of 40.degree. C or higher, 0.5 to 30% of an organic solvent
and 0.5 to 30% of water, based on the weight of the ink composition
(hereinafter referred to as "composition II"), and
(3) an ink composition erasable with a rubber eraser, the composition
comprising 2 to 90% of a pigment coated with a resin having a film-forming
temperature of 0.degree. C or higher, 1.5 to 55% of an emulsion
(calculated as solids), 0.5 to 30% of an organic solvent and 4.0 to 60% of
water, based on the weight of the ink composition (hereinafter referred to
as "composition III").
The term "minimum film-forming temperature" (or "MFT") used herein refers
to a minimum temperature for forming a coating film from an emulsion,
namely a threshold temperature above which a film can be formed but below
which a film can not be formed.
The compositions I, II and III will be described below in detail.
1. Composition I
Pigments useful for the erasable composition I of the invention are not
specifically limited. Pigments commonly employed for writing inks are
usable singly or at least two of them can be used in mixture. Examples of
usable pigments are shown below according to the color index (C.I.)
number.
Inorganic pigment
25 (a) Pigment Black 6, 7, 9, 10
(b) Pigment Red 101, 105, 106, 107, 108
(c) Pigment Blue 27, 28, 29, 35
(d) Pigment Green 17. 18, 19, 21
Organic pigment
5 (a) Pigment Black 1
(b) Pigment Red 1, 2, 3, 4, 5, 7, 9, 12, 22
(c) Pigment Blue 1, 2, 15, 16, 17
(d) Pigment Green 2, 7, 8, 10
The resin component for the erasable ink composition I of the invention is
selected for use from acrylic resins, acryl-styrene copolymer resins,
ethylene-vinyl acetate-vinyl chloride copolymer resins, acryl-vinyl
acetate copolymer resins, carboxylated butadiene-styrene rubber, styrene
resins and the like which have a film-forming temperature of 40.degree. C.
or higher. Preferred resins have a film-forming temperature of 50.degree.
C. or higher. The resins with a film-forming temperature of lower than
40.degree. C. partially form a resin film even at room temperature during
the storage of ink, or result in the formation of a resin film by the
frictional heat generated on rubbing of writing with a rubber eraser to
strengthen the adhesion between the writing and paper, thereby making
impossible erasure with the rubber eraser. These resins are commercially
available in the form of an emulsion having a solids concentration of
about 30 to about 60% by weight, and are therefore usable as they are.
When required, at least two of these resins can be used in mixture.
Organic solvents useful for the erasable ink composition I of the invention
are not specifically limited and can be any of solvents commonly employed
for writing inks. Examples of useful organic solvents are ethylene glycol,
propylene glycol, hexylene glycol and like alkylene glycols; diethylene
glycol, dipropylene glycol and like dialkylene glycols; polyethylene
glycol, polypropylene glycol and like polyalkylene glycols; glycerins;
etc. When required, two or more solvents can be used in mixture.
The proportions of the components for the erasable ink composition I of the
invention are required to fall in the following ranges based on the weight
of the composition.
The proportion of the pigment is 1 to 50%, preferably 5 to 30%. Less than
1% of the pigment used renders the ink unsuitable for use because of the
resulting low density of writing, whereas more than 50% of the pigment
used decreases the dispersion stability, making difficult the removal of
writing.
The proportion of the resin component, calculated as solids, is 3 to 50%,
preferably 10 to 45%. Less than 3% of the resin component used fails to
form a film containing a sufficient amount of particulate resin on the
surface of a writing sheet, making it impossible to completely erase the
writing by removing the particulate resin layer enclosing therein the
pigment. On the other hand, more than 50% of the resin component used
excessively increases the viscosity of the ink, making difficult the
release of ink from the container.
The proportion of the organic solvent is 0.5 to 50%, preferably 10 to 30%.
Less than 0.5% of the solvent used shortens the long-term shelf life of
the ink, whereas more than 50% of the solvent used increases the
permeability of ink with respect to paper so highly as to permit the
penetration of pigment into the paper, making complete erasure difficult.
The water is used in a proportion of 7 to 60% inclusive of the portion of
water derived from the resin component used in the form of an emulsion. In
case water is added to the portion of water resulting from the emulsion,
ion exchange water is used.
The erasable ink composition I of the invention can be prepared by an
optional method which can homogeneously disperse the components. Stated
more specifically, the ink is prepared, for example, by kneading the
pigment and the resin emulsion to obtain a pigment paste, adding an
organic solvent and water to the paste and stirring the mixture.
2. Composition II L- Pigments useful for the erasable ink composition II of
the invention can be any of pigments commonly used for writing inks. These
pigments are coated with a resin having a film-forming temperature of
40.degree. C. or higher. Useful common pigments may be those usable for
the composition I.
The resin component for coating such common pigment is selected, as is the
resin component for the composition I, from acrylic resins, acryl-styrene
copolymer resins, ethylene-vinyl acetate-vinyl chloride copolymer resins,
acryl-vinyl acetate copolymer resins, carboxylated butadiene-styrene
rubber, styrene resins and the like which have a film-forming temperature
of 40.degree. C. or higher. Preferred resins have a film-forming
temperature of 50.degree. C. or higher. The resins with a film-forming
temperature of lower than 40.degree. C. partially form a resin film even
at room temperature during the storage of ink, or result in the formation
of a resin film by the frictional heat generated on rubbing of writing
with a rubber eraser to provide a strong adhesion between the writing and
the paper, making impossible erasure with a rubber eraser.
The resin-coated pigment useful for the erasable ink composition II of the
invention can be easily obtained by conventional methods, e.g., by
homogeneously coagulating the pigment and the resin. The pigment : resin
ratio (weight ratio) of useful resin-coated pigment is approximately 40-95
: 60-5. Preferred particles of resin-coated pigment have a mean particle
size of about 0.1 to about 10 .mu.m in view of excellent stability to
dispersion in the ink composition, erasability, fluidity at the pen tip
and the like. When required, at least two of resin-coated pigments can be
used in mixture.
The organic solvents usable for the composition I can be used for the
composition II.
The proportions of the components for the erasable ink composition II
according to the invention need to fall in the following ranges based on
the weight of the composition.
The proportion of the resin-coated pigment is 2 to 90%, preferably about 10
to about 70%. Less 2% of the pigment used makes the ink unsuited for use
because of the resulting low density of writing, whereas more than 90%
thereof used decreases the dispersion stability, making erasure difficult.
The proportion of the organic solvent is 0.5 to 30%, preferably about 1 to
about 20%. Less than 0.5% of the organic solvent used shortens the
long-term shelf life of the ink, whereas over 30% thereof used so highly
increases the permeability of ink with respect to paper as to permit the
penetration of ink into paper, making complete removal difficult.
The proportion of the water is 0.5 to 30%, and ion exchange water is used.
The erasable ink composition II according to the invention can be prepared
by an optional method which can homogeneously disperse the components. For
example, the desired composition II can be formulated by stirring a
mixture of the resin-coated pigment, organic solvent and water until they
become homogeneously dispersed.
3. Composition III
The composition III contains a resin emulsion in addition to the same three
components as in the composition II. The foregoing resins useful for
coating the pigment can be employed as the resin in the emulsion. The
proportion of the resin emulsion is 1.5 to 55%, preferably 2 to 50%,
calculated as solids. If the resin is used in this proportion range, a
uniform coating of resin particles enclosing therein the pigment particles
is formed on the surface of a writing sheet, and the removal of the
pigment-enclosing resin coating assures and facilitates complete erasure
of writing. More than 55% of the resin component used excessively
increases the viscosity of ink, making difficult the flow of ink out of
the container. In view of using the emulsion, water is used in an amount
of 4 to 60% inclusive of the portion of water derived from the emulsion.
The ratio of the resin-coated pigment to the organic solvent is the same as
in the composition II.
The composition III is prepared by the same method as the composition II.
The erasable inks of the invention have a low viscosity (about 10 to about
100 cps: measuring conditions; an ELD-type viscometer, 3.degree. cone,
20.degree. C., 20 rpm), and an excellent storage stability so that they
can be used in the same manner as usual writing inks for ball point pens,
marking pens and so on unlike conventional erasable inks which require a
pressure-type container.
EFFECTS OF THE INVENTION
Since the erasable inks of the invention exhibit a low permeability with
respect to the surface of a writing sheet (e.g. paper) and the pigment is
retained within the layer of particulate resin formed on the surface of
the writing sheet, the writing can be extremely easily erased with a
rubber eraser. Further the erasable inks of the invention sustain the good
erasability for a long period because of their high storage stability.
EXAMPLES
25 Given below are Examples to clarify the features of the invention with
reference to the drawings.
FIG. 1 is a graph showing the viscosity of the inks prepared in the
Examples illustrative of the invention.
The word "parts" used in Examples are all by weight. The amount of the
resin is expressed in terms of the amount of the emulsion, and the amount
of the water in terms of the amount of ion exchange water added.
EXAMPLE 1
The erasable ink composition of the invention was prepared from the
following components.
______________________________________
Carbon black 5 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
80 parts
resin emulsion (*1)
Ethylene glycol 7 parts
Water 8 parts
______________________________________
Note:
*1 Trademark "Movinyl 970," 100.degree. C. in filmforming temperature, 40
in solids concentration, product of Hoechst Synthesis Co., Ltd.
In preparing the ink, the carbon black and the resin emulsion were kneaded
by a three-roll mill to obtain a pigment paste. Ethylene glycol and ion
exchange water were added to the paste and the mixture was stirred, giving
the ink of the invention.
Writing was produced using a ball point pen charged with the obtained ink.
The layer (writing) was dried and the dried writing was completely removed
on rubbing with a usual eraser.
Writing produced using a ball point pen charged with the obtained ink was
left to stand for 30 days at 25.degree. C. and tested for erasability in
the same manner as above. The writing was completely erased as in the
above test.
EXAMPLE 2
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 7 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
68 parts
resin emulsion (*2)
Glycerin 11 parts
Water 14 parts
______________________________________
Note:
*2 Trademark "Polysol AT2011," 100.degree. C. in filmforming temperature,
50% in solids concentration, product of Showa Highpolymer Co., Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 3
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 7 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
74 parts
resin emulsion (*3)
Propylene glycol 7 parts
Water 12 parts
______________________________________
Note:
*3 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 4
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 6 parts
(C.I. Pigment Black 7)
Acrylic resin emulsion (*4)
71 parts
Diethylene glycol 8 parts
Water 15 parts
______________________________________
Note:
*4 Trademark "Movinyl 742", 50.degree. C. in filmforming temperature, 46%
in solids concentration, product of Hoechst Synthesis Co., Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 5
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 5 parts
(C.I. Pigment Black 7)
Acryric resin emulsion (*5)
68 parts
Polyethylene glycol 12 parts
(molecular weight: 200)
Water 15 parts
______________________________________
Note:
*5 Trademark "Acryset llE", 50.degree. C. in filmforming temperature, 42%
in solids concentration, product of Japan Catalytic Chemical Industry Co.
Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 6
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 8 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
65 parts
resin emulsion (*6)
Glycerin 11 parts
Water 13 parts
______________________________________
Note:
*6 Same as in Example 2.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 7
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 9 parts
(C.I. Pigment Black 7)
Styrene resin emulsion (*7)
68 parts
Ethylene glycol 9 parts
Water 14 parts
______________________________________
Note:
*7 Trademark "Polysol C10," 100.degree. C. in filmforming temperature, 49
in solids concentration, product of Showa Highpolymer Co., Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 8
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 6 parts
(C.I. Pigment Black 7)
Acryl-vinyl acetate copolymer
72 parts
resin emulsion (*8)
Glycerin 9 parts
Water 13 parts
______________________________________
Note:
*8 Trademark "Polysol AT1000," 45.degree. C. in filmforming temperature,
50% in solids concentration, product of Showa Highpolymer Co., Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 9
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Carbon black 9 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
64 parts
resin emulsion (*9)
Ethylene glycol 12 parts
Water 15 parts
______________________________________
Note:
*9 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
COMPARATIVE EXAMPLE 1
The erasable ink for comparison was prepared from the following components.
______________________________________
Carbon black 7 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
70 parts
resin emulsion (*10)
Ethylene glycol 10 parts
Water 13 parts
______________________________________
Note:
*10 Trademark "Movinyl 748," 10.degree. C. in filmforming temperature, 45
in solids concentration, product of Hoechst Synthesis Co., Ltd.
Since the resin emulsion used had too a low film-forming temperature, a
resin film was formed on the surface of paper, causing the writing to
strongly adhere to the paper with the result that the writing formed from
the obtained ink was not removed with a rubber eraser.
COMPARATIVE EXAMPLE 2
The erasable ink for comparison was prepared from the following components.
______________________________________
Carbon black 8 parts
(C.I. Pigment Black 7)
Acryl-styrene copolymer
69 parts
resin emulsion (*11)
Glycerin 8 parts
Water 15 parts
______________________________________
Note:
*11 Trademark "Movinyl 670," 20.degree. C. in filmforming temperature, 45
in solids concentration, product of Hoechst Synthesis Co., Ltd.
Since the resin emulsion used had too a low film-forming temperature, a
resin film was formed on the surface of paper, causing the writing to
strongly adhere to the paper with the result that the writing formed from
the obtained ink was not removed with a rubber eraser.
EXAMPLE 10
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Permanent Red 4R 8 parts
(C.I. Pigment Red 3)
Acryl-styrene copolymer
75 parts
resin emulsion (*12)
Propylene glycol 8 parts
Water 9 parts
______________________________________
Note:
*12 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 11
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Phthalocyanine Blue 22 parts
(C.I. Pigment Blue 15)
Styrene resin emulsion (*13)
59 parts
Polyethylene glycol 7 parts
(Molecular weight: 400)
Water 12 parts
______________________________________
Note:
*13 Same as in Example 7.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 12
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components.
______________________________________
Phthalocyanine Green
20 parts
(C.I. Pigment Green 7)
Acryl-styrene copolymer
52 parts
resin emulsion (*14)
Diethylene glycol 7 parts
Water 15 parts
______________________________________
Note:
*14 Same as in Example 2
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 1.
EXAMPLE 13
The erasable ink of the invention was prepared from the following
components.
______________________________________
Resin-coated pigment (Black)
70 parts
Acryl-styrene copolymer
5 parts
resin emulsion (*15)
Ethylene glycol 5 parts
Water 20 parts
______________________________________
Note:
*15 Same as in Example 1.
The resin-coated pigment used in this example and to be used in Examples 14
to 22 was prepared by a homogeneously coagulating method using C. I.
Pigment Black 11 as a black pigment and acryl-styrene copolymer resin
emulsion (same as above) in equal amounts (calculated as solids). The
pigment particles had a mean particle size of about 1 .mu.m.
In preparing the ink, the resin-coated pigment and the resin emulsion were
kneaded by a three-roll mill to obtain a pigment paste. Ethylene glycol
and ion exchange water were added to the paste and the mixture was
stirred, giving the ink of the invention.
The obtained ink was charged into an ink-storing container, and writing was
produced. The writing was dried, and the dried writing was completely
removed on rubbing with a usual rubber eraser.
Further, the obtained ink was charged into an ink-storing container and
left to stand at 25.degree. C. for 30 days. Writing was produced and the
writing was tested for erasability in the same manner as above. The ink
was as erasable as above.
EXAMPLE 14
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
70 parts
Acryl-styrene copolymer
5 parts
resin emulsion (*16)
Ethylene glycol 5 parts
Water 20 parts
______________________________________
Note:
*16 Trademark "Movinyl 972," 100.degree. C. in filmforming temperature,
50% in solids concentration, product of Hoechst Synthesis Co., Ltd.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 15
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
76 parts
Acryl-styrene copolymer
9 parts
resin emulsion (*17)
Glycerin 4 parts
Water 11 parts
______________________________________
Note:
*17 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 16
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
70 parts
Acryl-styrene copolymer
5 parts
resin emulsion (*18)
Ethylene glycol 5 parts
Water 20 parts
______________________________________
Note:
*18 Same as in Example 2.
The obtained ink of had a higher erasability and higher storage stability
than the ink prepared in Example 1.
EXAMPLE 17
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
70 parts
Acryl-styrene copolymer
5 parts
resin emulsion (*19)
Ethylene glycol 5 parts
Water 20 parts
______________________________________
Note:
*19 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 18
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
65 parts
Acryl-styrene copolymer
14 parts
resin emulsion (*20)
Propylene glycol 7 parts
Water 14 parts
______________________________________
Note:
*20 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 19
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
56 parts
Acryl-styrene copolymer
23 parts
resin emulsion (*21)
Diethylene glycol 7 parts
Water 14 parts
______________________________________
Note:
*21 Same as in Example 14.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 20
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using
______________________________________
Resin-coated pigment
62 parts
Styrene resin emulsion (*22)
24 parts
Polyethylene glycol 5 parts
(molecular weight: 400)
Water 9 parts
______________________________________
Note:
*22 Same as in Example 7.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 21
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
10 parts
Acryl-styrene copolymer
58 parts
resin emulsion (*23)
Hexylene glycol 4 parts
Water 28 parts
______________________________________
Note:
*23 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 22
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components.
______________________________________
Resin-coated pigment
7 parts
Acryl-vinyl acetate copolymer
67 parts
resin emulsion (*24)
Ethylene glycol 4 parts
Water 22 parts
______________________________________
Note:
*24 Same as in Example 8.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 23
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 13 using the following components. The
resin-coated pigment used in this example was prepared by a homogeneously
coagulating method, using C.I. Pigment Red 101 as a red pigment and
acryl-styrene copolymer resin emulsion (same as below) in equal amounts
(calculated as solids). The pigment particles had a mean particle size of
about 0.7 .mu.m.
______________________________________
Resin-coated pigment
24 parts
Acryl-styrene copolymer
48 parts
resin emulsion (*25)
Ethylene glycol 9 parts
Water 19 parts
______________________________________
Note:
*25 Same as in Example 1.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 24
The erasable ink of the invention was prepared by carrying out the same
procedure as in Example 1 using the following components. The resin-coated
pigment used in this example was prepared by a homogeneously coagulating
method using C.I. Pigment Blue 27 as a blue pigment and styrene resin
emulsion (same as below) in equal amounts (calculated as solids). The
pigment particles had a mean particle size of about 2 .mu.m.
______________________________________
Resin-coated pigment
13 parts
Styrene resin emulsion (*26)
62 parts
Glycerin 10 parts
Water 15 parts
______________________________________
Note:
*26 Same as in Example 7.
The obtained ink had a higher erasability and higher storage stability than
the ink prepared in Example 13.
EXAMPLE 25
Each ink obtained above was tested for erasability according to the
erasability (rate of erasure) test prescribed in JIS S6227.
Table 1 b below shows the results.
The results show that the inks of the present invention prepared in the
Examples had much higher erasability than the inks prepared in the
Comparative Examples.
TABLE 1
__________________________________________________________________________
Example
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Comp.
1x.
2
__________________________________________________________________________
Rate of
85
84
86
79
81
85
83
81
84
83
84
85
89
93
94
93
93
98
97
96
95
97
93
94 35
41
erasure
(%)
__________________________________________________________________________
EXAMPLE 26
The viscosity of the inks obtained in Examples 1, 13 and 18 was measured
using an ELD-type viscometer with 3" cone at 20.degree. C.
FIG. 1 shows the relationship between the revolution (r.p.m.) and the
viscosity (cps).
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